Maryse Bonnière

Matthew-Wood Syndrome Is Caused by Truncating Mutations in the Retinol-Binding Protein Receptor Gene STRA6

Retinoic acid (RA) is a potent teratogen in all vertebrates when tight homeostatic controls on its endogenous dose, location, or timing are perturbed during early embryogenesis. STRA6 encodes an integral cell-membrane protein that favors RA uptake from soluble retinol-binding protein; its transcription is directly regulated by RA levels. Molecular analysis of STRA6 was undertaken in two human fetuses from consanguineous families we previously described with Matthew-Wood syndrome in a context of severe microphthalmia, pulmonary agenesis, bilateral diaphragmatic eventration, duodenal stenosis, pancreatic malformations, and intrauterine growth retardation. The fetuses had either a homozygous insertion/deletion in exon 2 or a homozygous insertion in exon 7 predicting a premature stop codon in STRA6 transcripts. Five other fetuses presenting at least one of the two major signs of clinical anophthalmia or pulmonary hypoplasia with at least one of the two associated signs of diaphragmatic closure defect or cardiopathy had no STRA6 mutations. These findings suggest a molecular basis for the prenatal manifestations of Matthew-Wood syndrome and suggest that phenotypic overlap with other associations may be due to genetic heterogeneity of elements common to the RA- and fibroblast growth factor-signaling cascades.

Analysis of human samples reveals impaired SHH-dependent cerebellar development in Joubert syndrome/Meckel syndrome

Joubert syndrome (JS) and Meckel syndrome (MKS) are pleiotropic ciliopathies characterized by severe defects of the cerebellar vermis, ranging from hypoplasia to aplasia. Interestingly, ciliary conditional mutant mice have a hypoplastic cerebellum in which the proliferation of cerebellar granule cell progenitors (GCPs) in response to Sonic hedgehog (SHH) is severely reduced. This suggests that Shh signaling defects could contribute to the vermis hypoplasia observed in the human syndromes. As existing JS/MKS mutant mouse models suggest apparently contradictory hypotheses on JS/MKS etiology, we investigated Shh signaling directly on human fetal samples. First, in an examination of human cerebellar development, we linked the rates of GCP proliferation to the different levels and localizations of active Shh signaling and showed that the GCP possessed a primary cilium with CEP290 at its base. Second, we found that the proliferation of GCPs and their response to SHH were severely impaired in the cerebellum of subjects with JS/MKS and Jeune syndrome. Finally, we showed that the defect in GCP proliferation was similar in the cerebellar vermis and hemispheres in all patients with ciliopathy analyzed, suggesting that the specific cause of vermal hypo-/aplasia precedes this defect. Our results, obtained from the analysis of human samples, show that the hemispheres and the vermis are affected in JS/MKS and provide evidence of a defective cellular mechanism in these pathologic processes.

Antenatal spectrum of CHARGE syndrome in 40 fetuses with CHD7 mutations

Background CHARGE syndrome is a rare, usually sporadic disorder of multiple congenital anomalies ascribed to a CHD7 gene mutation in 60% of cases. Although the syndrome is well characterised in children, only one series of 10 fetuses with CHARGE syndrome has been reported to date. Therefore, we performed a detailed clinicopathological survey in our series of fetuses with CHD7 mutations, now extended to 40 cases. CHARGE syndrome is increasingly diagnosed antenatally, but remains challenging in many instances. Method Here we report a retrospective study of 40 cases of CHARGE syndrome with a CHD7 mutation, including 10 previously reported fetuses, in which fetal or neonatal clinical, radiological and histopathological examinations were performed. Results Conversely to postnatal studies, the proportion of males is high in our series (male to female ratio 2.6:1) suggesting a greater severity in males. Features almost constant in fetuses were external ear anomalies, arhinencephaly and semicircular canal agenesis, while intrauterine growth retardation was never observed. Finally, except for one, all other mutations identified in our antenatal series were truncating, suggesting a possible phenotype–genotype correlation. Conclusions Clinical analysis allowed us to refine the clinical description of CHARGE syndrome in fetuses, describe some novel features and set up diagnostic criteria in order to help the diagnosis of CHARGE syndrome after termination of pregnancies following the detection of severe malformations.

High‐throughput sequencing of a 4.1 Mb linkage interval reveals FLVCR2 deletions and mutations in lethal cerebral vasculopathy

Rare lethal disease gene identification remains a challenging issue, but it is amenable to new techniques in high‐throughput sequencing (HTS). Cerebral proliferative glomeruloid vasculopathy (PGV), or Fowler syndrome, is a severe autosomal recessive disorder of brain angiogenesis, resulting in abnormally thickened and aberrant perforating vessels leading to hydranencephaly. In three multiplex consanguineous families, genome‐wide SNP analysis identified a locus of 14 Mb on chromosome 14. In addition, 280 consecutive SNPs were identical in two Turkish families unknown to be related, suggesting a founder mutation reducing the interval to 4.1 Mb. To identify the causative gene, we then specifically enriched for this region with sequence capture and performed HTS in a proband of seven families. Due to technical constraints related to the disease, the average coverage was only 7×. Nonetheless, iterative bioinformatic analyses of the sequence data identified mutations and a large deletion in the FLVCR2 gene, encoding a 12 transmembrane domain‐containing putative transporter. A striking absence of alpha‐smooth muscle actin immunostaining in abnormal vessels in fetal PGV brains, suggests a deficit in pericytes, cells essential for capillary stabilization and remodeling during brain angiogenesis. This is the first lethal disease‐causing gene to be identified by comprehensive HTS of an entire linkage interval. Hum Mutat 31:1–8, 2010.

Clinical, genetic and neuropathological findings in a series of 138 fetuses with a corpus callosum malformation.

BACKGROUND Corpus callosum malformation (CCM) is the most frequent brain malformation observed at birth. Because CCM is a highly heterogeneous condition, the prognosis of fetuses diagnosed prenatally remains uncertain, making prenatal counseling difficult. METHODS AND RESULTS We evaluated retrospectively a total of 138 fetuses, 117 with CCM observed on prenatal imaging examination, and 21 after postmortem autopsy. On ultrasound and/or magnetic resonance imaging, CCM was either isolated (N = 40) or associated with other neurological (N = 57) or extra cerebral findings (N = 21/20, respectively). RESULTS Most fetuses (N = 132) remained without a diagnosis at the time of pregnancy termination. This emphasizes the need to establish a neuropathological classification and to perform a genomic screening using comparative genomic hybridization. A neuropathological examination performed on 138 cases revealed a spectrum of CCMs, classified as follows: agenesis of corpus callosum (55), CC hypoplasia (30), CC dysmorphism (24), and CCM associated with a malformation of cortical development (29). Of interest, after fetopathological examination, only 16/40 malformations were classified as isolated, highlighting the importance of the autopsy following termination of pregnancy. Among the 138 cases, the underlying etiology was found in 46 cases: diabetes (one case), cytomegalovirus infection (one case), 23 chromosome abnormalities, and 21 mendelian conditions. CONCLUSION In our series of 138 cases of CCM, prenatal and postmortem examinations identified a variety of genetic causes. However, no diagnosis could be established in 67% of cases. The classification based on the underlying neurodevelopmental defects paves the way for further genetic studies and genotype-phenotype correlations.

Matthew‐Wood syndrome: Report of two new cases supporting autosomal recessive inheritance and exclusion of FGF10 and FGFR2

We describe two fetal cases of microphthalmia/anophthalmia, pulmonary agenesis, and diaphragmatic defect. This rare association is known as Matthew‐Wood syndrome (MWS; MIM 601186) or by the acronym “PMD” (Pulmonary agenesis, Microphthalmia, Diaphragmatic defect). Fewer than ten pre‐ and perinatal diagnoses of Matthew‐Wood syndrome have been described to date. The cause is unknown, and the mode of transmission remains unclear. Most cases have been reported as isolated and sporadic, although recurrence among sibs has been observed once. Our two cases both occurred in consanguineous families, further supporting autosomal recessive transmission. In addition, in one family at least one of the elder sibs presented an evocatively similar phenotype. The spatiotemporal expression pattern of the FGF10 and FGFR2 genes in human embryos and the reported phenotypes of knockout mice for these genes spurred us to examine their coding sequences in our two cases of MWS. While in our patients, no causative sequence variations were identified in FGF10 or FGFR2, this cognate ligand‐receptor pair and its downstream effectors remain functional candidates for MWS and similar associations of congenital ocular, diaphragmatic and pulmonary malformations.

Stress-induced unfolded protein response contributes to Zika virus-associated microcephaly

Accumulating evidence support a causal link between Zika virus (ZIKV) infection during gestation and congenital microcephaly. However, the mechanism of ZIKV-associated microcephaly remains unclear. We combined analyses of ZIKV-infected human fetuses, cultured human neural stem cells and mouse embryos to understand how ZIKV induces microcephaly. We show that ZIKV triggers endoplasmic reticulum stress and unfolded protein response in the cerebral cortex of infected postmortem human fetuses as well as in cultured human neural stem cells. After intracerebral and intraplacental inoculation of ZIKV in mouse embryos, we show that it triggers endoplasmic reticulum stress in embryonic brains in vivo. This perturbs a physiological unfolded protein response within cortical progenitors that controls neurogenesis. Thus, ZIKV-infected progenitors generate fewer projection neurons that eventually settle in the cerebral cortex, whereupon sustained endoplasmic reticulum stress leads to apoptosis. Furthermore, we demonstrate that administration of pharmacological inhibitors of unfolded protein response counteracts these pathophysiological mechanisms and prevents microcephaly in ZIKV-infected mouse embryos. Such defects are specific to ZIKV, as they are not observed upon intraplacental injection of other related flaviviruses in mice.The mosquito-borne ZIKA virus triggers microcephaly in human newborns. The authors report that the microcephaly results from induction of endoplasmic stress that interferes with generation and survival of projection neurons in the cerebral cortex.

Early neonatal death and congenital left coronary abnormalities: ostial atresia, stenosis and anomalous aortic origin.

BACKGROUND Congenital left coronary artery abnormalities such as ostial stenosis or atresia are extremely rare. Diagnosis in the neonate has not been reported. AIMS To describe five neonates with left coronary artery orifice abnormalities and discuss pathophysiology, diagnosis and treatment options, with a focus on the importance of autopsy in unexpected neonatal death. METHODS Retrospective assessment of medical files of neonates with left coronary abnormalities seen during a 12-year period (2000-2012). RESULTS Three neonates with anatomical (n=2) and functional (n=1) left coronary stenosis and two neonates with ostial atresia were identified. The three infants with coronary stenosis died within minutes to days after birth because of cardiac failure refractory to intensive care treatment; at autopsy, left coronary ostial stenosis (n=2) and high take-off with acute angle origin and tangential vertical course (n=1) were diagnosed. The fourth neonate was in cardiac failure due to critical aortic stenosis; left coronary ostial atresia was diagnosed during an emergency catheter procedure and the infant died after aortic valve dilatation. The fifth infant had a cardiac arrest on the third day of life; she was diagnosed with left coronary ostial atresia by coronary angiography and died during attempted revascularization surgery at 2 weeks of life. CONCLUSION Congenital coronary ostial abnormalities can lead to severe heart failure and unexpected neonatal death. Systematic examination of the coronary arteries should be part of any neonatal autopsy. Coronary angiography remains the diagnostic method of choice despite advances in non-invasive imaging. Revascularization surgery seems indicated in symptomatic children based on small patient series.

A practical approach to the examination of the malformed fetal brain: impact on genetic counselling.

&NA; Birth defects of the brain result from malformation and disruptions. They remain an important cause of childhood morbidity and mortality. Effective treatments are scarce and prevention strategies limited. As aetiological screening is costly and uncertain, genetic counselling remains empirical in most cases. A pathological study of the malformed brain is the best approach to establish the diagnosis of a brain malformation. It relies on a thorough description of the brain, including its size, external pattern and/or internal configuration. When evaluating a malformed brain two major factors should be considered: (1) malformations result from an arrest of the development at a given time, interfering with subsequent stages of development, leading to a sequence of malformations where the ‘primary event’ should be distinguished from ‘secondary changes’; (2) there is no obvious causal relationship when the final morphology of the central nervous system is considered. For example, mutations in different genes involved in a signalling pathway may result in a similar pattern of malformations. In addition, signalling pathways may be a possible target of toxic agents, mimicking malformations caused by genetic factors. A precise diagnosis will allow rational aetiological screening, with direct benefit for the family, which may serve other families. In addition, it helps to establish a quality assurance process for medical practice, collect solid epidemiological data and conduct research studies. Because of discrepancies observed between human diseases and animal models, research on human material is mandatory. This requires collection of organs, tissues and cells within a legal and ethical framework.

In utero ultrasound diagnosis of corpus callosum agenesis leading to the identification of orofaciodigital type 1 syndrome in female fetuses

OFD1 syndrome is a rare ciliopathy inherited on a dominant X‐linked mode, typically lethal in males in the first or second trimester of pregnancy. It is characterized by oral cavity and digital anomalies possibly associated with cerebral and renal signs. Its prevalence is between 1/250,000 and 1/50,000 births. It is due to heterozygous mutations of OFD1 and mutations are often de novo (75%). Familial forms show highly variable phenotypic expression. OFD1 encodes a protein involved in centriole growth, distal appendix formation, and ciliogenesis.